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From "Mikhail Yakshin (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-5167) MultipleOutputs should use newer Hadoop serialization interface since 0.19
Date Wed, 04 Feb 2009 17:18:00 GMT
MultipleOutputs should use newer Hadoop serialization interface since 0.19
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                 Key: HADOOP-5167
                 URL: https://issues.apache.org/jira/browse/HADOOP-5167
             Project: Hadoop Core
          Issue Type: Bug
          Components: mapred
    Affects Versions: 0.19.0
         Environment: Environment-independent issue
            Reporter: Mikhail Yakshin


We have a system based on Hadoop 0.18 / Cascading 0.8.1 and now I'm trying to port it to Hadoop
0.19 / Cascading 1.0. The first serious problem I've got into that we're extensively using
MultipleOutputs in our jobs dealing with sequence files that store Cascading's Tuples.

Since Cascading 0.9, Tuples stopped being WritableComparable and implemented generic Hadoop
serialization interface and framework. However, in Hadoop 0.19, MultipleOutputs require use
of older WritableComparable interface. Thus, trying to do something like:

{noformat}
MultipleOutputs.addNamedOutput(conf, "output-name",
MySpecialMultiSplitOutputFormat.class, Tuple.class, Tuple.class);
mos = new MultipleOutputs(conf);
...
mos.getCollector("output-name", reporter).collect(tuple1, tuple2);
{noformat} 

yields an error:

{noformat}
java.lang.RuntimeException: java.lang.RuntimeException: class
cascading.tuple.Tuple not org.apache.hadoop.io.WritableComparable
       at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:752)
       at org.apache.hadoop.mapred.lib.MultipleOutputs.getNamedOutputKeyClass(MultipleOutputs.java:252)
       at org.apache.hadoop.mapred.lib.MultipleOutputs$InternalFileOutputFormat.getRecordWriter(MultipleOutputs.java:556)
       at org.apache.hadoop.mapred.lib.MultipleOutputs.getRecordWriter(MultipleOutputs.java:425)
       at org.apache.hadoop.mapred.lib.MultipleOutputs.getCollector(MultipleOutputs.java:511)
       at org.apache.hadoop.mapred.lib.MultipleOutputs.getCollector(MultipleOutputs.java:476)
       at my.namespace.MyReducer.reduce(MyReducer.java:xxx)
{noformat}

MultipleOutputs should eventually be ported to use more generic Hadoop serialization, as I
understand.

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